Abstract: A blower control system for the evaporator blowers employed in the climate conditioning system for a motor vehicle passenger compartment. Maximum blower efficiency for the various conditions of operation is attained by using blowers having two operating speeds, the proper operating speed in this invention being dictated by engine water temperature, outside temperature, passenger loading, and system return air temperature. The passenger load sensing circuit has a pressure switch associated with the suspension springs system of the vehicle for switching the blowers from low to high speed operation when load conditions so dictate. A zero speed controller is used to lock in a blower speed selected when loading or unloading passengers to avoid unwanted repetitive cycling of the system.

Abstract: The brake, including a brake housing, is characterized by a housing having an inwardly extending flange forming a pressure chamber with an annular piston slidably positioned in the brake housing, and the annular piston and a secondary piston are operatively associated with opposed sides of the inwardly extending flange to form pressure chambers therewith for individual actions in the brake. Spring means operatively engage the secondary piston for moving the same into operative pressure braking position for fail safe braking operation. Air pressure is supplied to the two pressure chambers or cylinders for controlling brake release and braking action.